Lifestyle changes for a healthy pregnancy: Caffeine, exercise, and more

When newly pregnant or soon-to-be-pregnant patients ask about alcohol, exercise, caffeine, and diet drinks, be sure you know the data.

Women in early pregnancy and those attempting conception are often concerned with altering their lifestyles to achieve and maintain a healthy pregnancy. Patients often ask ob/gyns for recommendations about caffeine intake, exercise, alcohol consumption, and use of artificial sweeteners. In addition to quantity, the question of timing arises: When is the appropriate time for a woman to alter her lifestyle—before conception or after pregnancy is established?

Caffeine intake: How much is really too much?

Caffeine crosses the placenta, and caffeine clearance during pregnancy is slower than in the nonpregnant state.1,2 Numerous older studies suggested that caffeine use in pregnancy may be associated with spontaneous miscarriage.3,4 However, more recent, better-designed studies have clarified this association. In a large retrospective analysis, 562 Swedish women who had experienced a spontaneous abortion at 6 to 12 weeks’ gestation were surveyed for caffeine intake and compared with 953 pregnant women with no history of miscarriage. The authors found a significant increase in miscarriage only in those who consumed more than 500 mg of caffeine daily.5

To try to alleviate patient recall, researchers measured serum paraxanthine, a biologic marker of caffeine consumption, in 591 women with a history of miscarriage and 2558 who had a live birth.6 Mean paraxanthine levels were higher in women with miscarriage than in the control group (752 ng/mL vs 583 ng/mL, P<0.001) after adjusting for confounders. However, only exceedingly high serum paraxanthine levelsâ¨(>1845 ng/mL) were associated with an increased incidence of miscarriage at fewer than 100 days’ gestation (adjusted odds ratio [aOR], 2.1; 95% confidence interval [CI], 1.2-3.6). A serum paraxanthine level of 1845 ng/mL is equivalent to approximately 6 or more cups of coffee per day consumed by a nonsmoker and 11 cups of coffee per day consumed by a smoker.6

More recently, prospective studies have further investigated the relationship between caffeine consumption and pregnancy loss. In a cohort study, approximately 2400 pregnancies in 3 cities in the southern United States were examined, and participants reported low to moderate caffeine consumption. The authors noted no significant increase in risk of miscarriage associated with caffeine consumption.7 This finding was echoed in a Danish study of 4443 women with miscarriage, 565 of whom consumed Letigen, a weight-loss medication containingâ¨200 mg of caffeine and 20 mg of ephedrine. No increased risk of miscarriage was noted among women using Letigen (hazard ratio [HR], 1.1; 95% CI, 0.8-1.6).8

Conversely, another study of 1063 women residing in San Francisco, California, found a dose-dependent increase in miscarriage. Daily consumption of 200 mg of caffeine was associated with a 2.79 adjusted hazard ratio (95% CI, 1.46-5.34) for pregnancy loss after 8 weeks’ gestation.9 A Danish study of 330 women with miscarriage showed an increase in pregnancy loss in those who consumed more than 375 mg of caffeine daily (aOR, 2.21; 95% CI, 1.53-3.18).10 Consumption of less than 200 mg of caffeine daily is a reasonable recommendation because evidence is scarce for increased miscarriage at that dose.

Recent large, prospective studies have refuted this idea and found no relationship between caffeine consumption and preterm birth.11,12 Similarly, no significant increase in IUGR was observed with moderate (<200 mg) caffeine consumption in multiple large, prospective studies.11-13 Based on these data, moderate caffeine consumption appears to be safe in pregnancy. As a result, the American College of Obstetricians and Gynecologists recommends limiting caffeine intake during pregnancy to less than 200 mg daily.14

Studies addressing infertility and caffeine intake have been conflicting. Time to conception and caffeine consumption, ranging from 0 to more than 2 beverages per day, were reported in 2817 postpartum women in the United States. No evidence was found of adverse effects of caffeine.15 Conversely, a European study of more than 3000 subfertile women found a dose-dependent relationship between caffeine consumption and time to pregnancy. Mean time to pregnancy was 6.5 months in those who consumed up to 100 mg/day of caffeine compared with 8.9 months in the greater-than-500-mg group.16

Earlier studies did not separate smokers and nonsmokers among the caffeine drinkers, which may have introduced bias. A Danish study of 423 couples evaluated caffeine consumption, including all beverages and chocolate, and its effect on fecundability, separating smokers from nonsmokers. No significant association was found between fecundability and intake of any source of caffeine, even at high levels (>700 mg/day).17 Based on these and other studies, it is reasonable for women attempting conception to follow the same caffeine restrictions as recommended for those already pregnant, that is, limiting daily intake to less than 200 mg.

The Centers for Disease Control and Prevention recommends 30 minutes of daily moderate exercise for general health and well-being in nonpregnant individuals. This recommendation has been extrapolated to pregnant women because regular exercise has been shown to reduce the incidence of gestational diabetes, particularly in obese women.18 Certain types of physical activity—contact sports and sports associated with a higher incidence of falls (eg, gymnastics, horseback riding, downhill skiing)—pose risks to pregnant women.

With the increased popularity of exercise in pregnancy over the last decade, concern arose about a possible increase in miscarriage with sustained, vigorous activity. A European study of more than 92,000 women addressed this issue, comparing pregnant women who engaged in varying amounts of weekly exercise with different intensities.19 The authors found a dose-response association between risk of miscarriage and exercise duration. Compared with women who engaged in no weekly exercise, those with 420 or more minutes of exercise per week (or 1 hour 7 days per week) had an adjusted hazard ratio of 3.1 (95% CI, 2.0-4.6) for miscarriage at fewer than 11 weeks’ gestation. The hazard ratios for those engaging in exercise forâ¨150 to 269 minutes and 270 to 419 minutes per week were 2.2 (95% CI, 1.7-2.8) and 2.7 (95% CI, 1.9-3.7), respectively. No significant increase in miscarriage was demonstrated in women who reported exercising 45 to 74 minutes per week. The study also compared time of miscarriage as it relates to exercise duration, finding no increase in miscarriage from 19 to 22 weeks’ gestation in women with even the longest exercise durations.

Moderate physical activity also appears to have no deleterious effects on birth weight and length of gestation after the first trimester. A randomized trial performed with previously sedentary pregnant Norwegian women evaluated the effect of supervised aerobic dance and strength training on pregnancy outcomes beginning after the first trimester. No difference was seen between the 2 groups in mean birth weight or length of gestation.20 Although mild to moderate exercise does not appear to have deleterious effects on pregnancy beyond the first trimester, taken together, these studies suggest that vigorous, sustained exercise may have negative effects on early pregnancy. Based on the data currently available and in the absence of medical contraindications, it seems reasonable to recommend regular moderate exercise while avoiding vigorous, sustained exercise to pregnant women as a way to attain health benefits while minimizing complications. Women in the first trimester of pregnancy who are engaged in sustained, high-intensity activity might consider attenuating their exercise until after 12 weeks’ gestation.

Alcohol consumption: When to stop?

The American Academy of Pediatrics has long recommended cessation of alcohol use during pregnancy because of the increased risk of abnormal fetal development.21 Ethanol is a known teratogen, with a spectrum of neurological and physical abnormalities.22-24 The optimum time for alcohol cessation has not been well defined. Should a woman discontinue all alcohol use while attempting conception or solely during/after ovulation? One European study of 1769 postpartum women indicated no decrease in fertility among women who reported alcohol consumption prior to conception.25 This study has been criticized because only women who delivered a newborn were interviewed, omitting those unable to conceive.

In a Danish study, 368 infertile, nonpregnant women were assessed for alcohol use and compared with nulliparous women not experiencing infertility. Alcohol consumption was associated with infertility in women aged older than 30 years, but not in younger women (aHR, 2.26; 95% CI, 1.19-4.32).26 More recently, a prospective Swedish study of 7393 women observed an increase of infertility in women who consumed 2 alcoholic beverages daily (relative risk [RR], 1.59; 95% CI, 1.09-2.31) compared with those consuming less than 1 drink per day (RR, 0.64; 95% CI, 0.46-0.90).27

Moreover, alcohol use also appears to negatively impact pregnancy rates in women undergoing fertility treatment. A total of 2545 women undergoing in vitro fertilization reported their alcohol intake. Live birth rates were decreased in those who drank 4 or more alcoholic beverages per week (OR, 0.84; 95% CI, 0.71-0.99). When both partners consumed 4 or more alcoholic beverages per week, the observed decrease was even more dramatic (OR, 0.79; 95% CI, 0.66-0.96).28 Based on the current data, alcohol consumption may have a negative effect on fertility. Given the above findings, the American Society for Reproductive Medicine recommends limiting alcohol consumption to less than 2 drinks per day while attempting conception.29

Artificial sweeteners

Artificial sweeteners (saccharin, aspartame, sucralose, and stevia) have become ubiquitous in the American diet. Animal experiments in the 1980s raised concern for possible carcinogenesis when saccharin was consumed in large quantities,30 which led ob/gyns to recommend avoiding this compound in pregnancy. Aspartame entered the food market in the late 1970s, and multiple safety studies showed no adverse health effects or increase in fetal anomalies in normal individuals.31,32

Individuals with phenylketonuria are cautioned that aspartame consumption in large quantities can increase serum phenylalanine levels, leading to toxicity. In addition, aspartame does not readily cross the placenta, making teratogenesis unlikely.32 Rodent studies illustrated no effect of aspartame consumption on reproduction or neonatal development in rodents, but human studies are lacking.33,34

A newer artificial sweetener, sucralose, a substituted disaccharide, also appears to be safe to consume during pregnancy based on a number of animal studies.35-38 Less is known about the safety of steviol glycosides, products generated from the South American plant Stevia rebaudiana. To date, animal experiments have demonstrated no adverse effects on fertility, gestation length, survival, and development of offspring.39

One human study addressed consumption of artificially sweetened beverages and preterm delivery based on self-report of more than 60,000 women.40 Daily consumption of artificial sweeteners showed a mild association with preterm delivery when compared with no consumption, but a similar effect was observed in women who drank sugar-sweetened beverages (aOR, 1.15; 95% CI, 1.01-1.32 and aOR, 1.13; 95% CI, 0.93-1.37, respectively). In general, moderate consumption of artificial sweeteners appears to be safe in pregnancy and when attempting conception, while avoidance of saccharin is recommended.

Summary

Recommendations for dietary intake of caffeine, alcohol, and artificial sweeteners for patients attempting conception mirror those for pregnant patients (Table 1). Moderate amounts of caffeine (Table 2)41 and artificial sweeteners appear to be safe, although no threshold dosage has been determined for adverse fertility effects. Alcohol consumption in pregnancy should be avoided, and excessive alcohol intake may lead to decreased fertility.

Moderate exercise in pregnancy appears to be safe, but women engaging in sustained, vigorous exercise may consider attenuated activity, especially during the first trimester.

Obesity before and during pregnancy

Prenatal nutrition clearly impacts short- and long-term health, but many scientific questions about it remain unanswered because performing high-quality scientific research in pregnancy is challenging. The critical windows of when nutrition may impact development often are unknown; many physiological changes occur over the course of normal pregnancy; maternal adaptation to pregnancy is widely varied; experimentation during human pregnancy is associated with ethical and practical issues; and good animal models that can be directly extrapolated to humans are lacking.

In the past 25 years, the prevalence of obesity—defined as prepregnancy body mass index (BMI) >30 kg/m2—has doubled, to a frequency of more than 30% in the adult population. Obesity contributes to many complications of pregnancy, including miscarriage, hypertension and preeclampsia, diabetes, fetal macrosomia, anomalies, stillbirth, cesarean delivery, and complications of cesarean delivery (excessive blood loss, infection, wound separation). Births of small-for-gestational-age infants are increased among women whose weight gain is below the Institute of Medicine’s BMI-based recommendations. I generally advise obese and overweight patents that the closer their prepregnancy weight is to the normal range (BMI, 18.5 to 24.9 kg/m2), the lower their risk of obesity-related complications.

Ideally, weight loss should be achieved by nonsurgical means. Case reports have identified complications in pregnancy after gastric bypass surgery, particularly in relation to intestinal obstruction and postoperative adhesions. Care should be taken in managing such patients when they present with abdominal pain. Women who experience emesis or inappropriate weight loss following gastric banding may need referral to a bariatric surgeon for adjustment of the bands. Furthermore, the American College of Obstetricians and Gynecologists suggests assessment of vitamin B12, folate, iron, and calcium levels in women who have undergone bariatric surgery and possible supplementation. If nutritional deficits are suspected, serial ultrasounds for fetal growth may be indicated.

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